I'm reading "Meaning and the English Verb" by Geoffrey Leech and in the paragraph §113 on page 71 he states the following:

§113:

First, the ways of referring to the future dealt with in this chapter illustrate the point made in §5: that the Present tense, from the semantic point of view as well as syntactically, would be best described as 'non-past'.

§5:

However, in English the major formal distinction of Present and Past tenses can be associated with two major TIME ZONES, 'past' and 'non-past', so that future time is subsumed under 'non-past'. This helps to explain why English, which does not have a Future tense as such, uses Present tense to express future time.

I know what he means by "from the semantic point of view", but I do not understand what he means by "syntactically" in this context.

So what does it mean when he says that "The Present tense would be syntactically best described as 'non-past'"?

If I haven't given enough information on §113, this is the full version:

§113:

First, the ways of referring to the future dealt with in this chapter illustrate the point made in §5: that the Present Tense, from the semantic point of view as well as syntactically, would be best described as 'non-past'. We have seen that all these future-referring constructions are variations on the Present Tense, with the very minor exception of the future subordinate use of the Past (see §102c) - even including the 'non-past' modal auxiliaries will / shall, to which we turn again in the next chapter. In other words, the Present Tense, in a broad sense, encompasses both present and future domains of time.